Figure 2

Concurrent absence of ARID1A and ARID1B expression in ARID1A/ARID1B co-mutated dedifferentiated carcinoma. The ARID1A and ARID1B immunostaining results of a representative case of ARID1A/ARID1B co-mutated dedifferentiated endometrial carcinoma (case 25, harbouring frameshift mutations involving both ARID1A and ARID1B) are illustrated. This tumour contained low-grade endometrioid (a) and undifferentiated carcinoma components (b). ARID1A expression was absent in the tumour cells in both the endometrioid (c) and the undifferentiated components (d). ARID1B expression was present/intact in the endometrioid component (e) but was absent in the undifferentiated tumour component (f). The background stromal cells showed intact expression of ARID1A and ARID1B.